package com.wanxi.generic;

import java.util.ArrayList;

public class WildCard {
    public static void main(String[] args) {
        ArrayList<? extends Number> list = new ArrayList<Integer>();
        ArrayList<Integer> aa = new ArrayList<>();
        ArrayList<Double> dd = new ArrayList<>();
        list = aa;
        list=dd;
        for (int i = 0; i < list.size(); i++) {
            
        }
        ArrayList<? super Number> lista = new ArrayList<Object>();
    }
}
